1. Field
The present disclosure relates generally to communication, and more specifically to techniques for originating a call in a communication network.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple-access networks capable of supporting communication for multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
Services provided by wireless communication networks can include the ability to make and receive calls including voice calls and emergency voice calls and the ability to send and receive data including data transmitted using the Internet Protocol (IP). To make and receive voice calls with efficient usage of network resources (e.g. wireless spectrum and wireline signaling and transmission lines), networks and terminals may support Voice over IP (VoIP) for normal calls and for emergency calls. In the case of emergency VoIP calls, networks that support radio access according to 3GPP and 3GPP2 standards (which includes networks that employ GSM, WCDMA, cdma2000 EvDO and LTE) may employ a solution in which support is provided using the IP Multimedia Subsystem (IMS) according to 3GPP Technical Specification (TS) 23.167 for Release 8 which is a publicly available document. When this solution is used, the VoIP emergency call is sometimes referred to as an IMS Emergency Call as call control and call signaling is supported by the IMS in the network (also known as the visited network) that is serving the user's terminal. In this context, a terminal may also be known as a mobile station or user equipment (UE).
A user equipment may be invoked by a user to place a VoIP emergency call with a wireless network, which may or may not be a home network with which the user has service subscription. The UE may go through several phases, such as registration and call establishment, in order to originate the VoIP emergency call. The UE may register with the wireless network so that the UE can be authenticated to the wireless network and the wireless network can obtain pertinent information such as verified identification information and a verified call back number. The UE may then perform call establishment in order to connect the call to an appropriate entity, e.g., a Public Safety Answering Point (PSAP), which can service the emergency call.
If a subscriber does not have wireless access at the time an emergency call is dialed (e.g. the user has just powered on the phone before dialing) or if the user has access to a data only network without voice call capability (e.g. has internet access via a WLAN) then the user's expectation of an emergency call succeeding and the legal requirements for some Voice Service Provider (VSP) supporting the emergency call may both be significantly lower than if the user is already accessing a voice capable network (e.g. a 3GPP voice capable Visited Public Land Mobile Network (VPLMN)) at the time the emergency call is dialed.
One problem is that in many cases, the VSP accessed by the user will not be local to the user's current location. For example, the user may be in a roaming situation and accessing a Home Public Land Mobile Network (H-PLMN) or some other remote VSP using direct IP access (e.g. from a WLAN or some other data only access network). In that case, the VSP may not be able to establish an emergency call to a suitable local PSAP (i.e. a PSAP local to the user) and there may be no local VSP (e.g. 3GPP VPLMN) already being accessed by the user to fall back to.
The serving VSP may then reject an attempt to establish an IMS emergency call (e.g., according to the 3GPP solution in TS 23.167, by returning a SIP 380 alternative service response to the UE) leaving the UE to search around for some alternative—e.g. via scanning for VSPs accessible from its current Internet Protocol Connectivity Access Network (IP-CAN) or by performing a radio search for other wireless IP-CANs. But that is hardly a reliable solution.
Additionally, the current solution for IMS Emergency calls in 3GPP Technical Specification (TS) 23.167 explicitly references and allows use of a 3GPP Control plane location solution and an Open Mobile Alliance (OMA) Secure User Plane Location (SUPL), but other possible location solutions are not explicitly supported.
Therefore, improved apparatus and methods for extended call establishment and location support for an IMS emergency call are desired.